This invention relates to a mechanical low pressure tire indicator which produces an audible warning when pressure in a tubeless pneumatic tire is low. The problem of low or inadequate tire pressure, and the detection of this problem, is manifest. Several concerns, such as poor fuel economy, increased tire wear, and impaired handling of the motor vehicle are all direct results of inadequate tire pressure. The present invention improves upon the prior art by providing a reliable, simple, and inexpensive means of indicating low tire pressure.
The present invention confronts the problem of low pressure detection by utilizing a spring device and hammer designed to strike the inner surface of a wheel hub when activated, thus producing an audible warning of low tire pressure. The invention has three main components; a spring device, a replaceable and adjustable rocker arm with an end roller on one end and a hammer on the other end. The installation and production costs are likely to be far less expensive than similar devices, particularly those that are electrical.
The invention disclosed in the prior art, for example, U.S. Pat. No. 4,476,455 (Kawakami), includes a shielding case mounted on the rim of a wheel and a rocking rod. The rocking rod has a first end contained within the shielding case and a second end extending into the tire and ending at a spaced distance from the inner surface of the tire tread. When tire pressure is low, the first end strikes the shielding case upon each wheel revolution, producing an audible warning of low tire pressure. The disadvantage of this device is in the durability and replaceability of the rocking rod. A tire in a condition of extreme low pressure would inevitably damage, if not destroy, the rocking rod and/or case shield, requiring replacement of the entire device.
The warning device disclosed in U.S. Pat. No. 4,353,322 (Weglin) is similarly deficient. Although the device fits within the wheel hub in such a way as to prevent damage when there is low or no tire pressure, the device contains a much more intricate assembly than that of the present invention. The Welgin device has many component parts, thereby increasing the risk of premature failure due to failure of an essential component. Replacement of an internal part would certainly be impractical.